I've tested each of these flower-care tips and can guarantee that you don't need a green thumb to follow these simple "rules" of thumb ...
Buzz's Top 10 Flower-Care Tips

1. Start with a container that gives your flowers room to breathe - who likes to walk around all day in shoes that are two sizes too small?
2. Make sure the container is clean. Dirt and other goo won't help your flowers look and feel their best.
3. Cut about an inch off the stems, and re-cut every few days. Stems are just like straw wrappers - you have to cut a bit off the bottom to let the flowers drink.
4. Cut stems under water to prevent air bubbles from sealing off the openings.
5. Use a sharp tool like a knife to cut stems - when was the last time you tried shaving with a dull razor?
6. Feed your flowers - fasting is bas for their health. Fill the container with warm water, and add commercial flower food.
7. Remove leaves that would otherwise be submerged in vase water - holding their breath under water can't be good for them.
8. Place your flowers in a spot that's not too hot, cold or drafty. After all, flowers can't grab a jacket or run for the shade.
9. Keep flowers fresh. Remove leaves and petals that fall in, and change water that looks cloudy.
10. Remove flowers that begin to fade. If only a few blossoms remain, transfer them to a smaller container, or add a couple of fresh stems to the bunch.